Discrete positioning mechanism



Aug. 9, 1960 M Et FREEMAN DISCRETE PosITloNING MECHANISM Filed June 25,1959 MARSHALL E. FREMAN ATTORNEY United States Patent DISCRETE PosmoNlNGMECHANISM Y. A* Marshall E. Freeman, San Jose, Calif.; assignor tonternational Business Machines Corporation, New York,

vN .Y., a corporationof New York Filed June 25 1.959, Ser.l No.'822,963f6 Claims. (ci. 121-38) This invention, relates in general topositioning devices, andin particular to pressure responsive devices forpositioningp a member at a selected one of aplurality of discretepositions. f

The prior art has suggested various arrangements for positioning amember selectively at one'of aplurality of discrete positions. In oneknown arrangement referredto the art as a cylinder adder, a number oflconven-y tional cylinder-piston units are arranged so -that each.`cylinder may be supplied withfluid pressure to move its associatedpiston between a pair of stops separated a predetermined ldistance.yUsually in these arrangements the predetermined distance between stopsfor each unit is dierent forming, for example, a mathematicalprogression such as 1 2, 4 and 8. By connecting each piston with vtheadjacent cylinder and the member to be positioned to the last piston, itvmllbe seen that any one. of a plurality of positions may be obtainedmerely by selectively actuating 4the units in various combinations.

Withconyentional cylinder-piston units it is desirable.

tol makethe piston land correspond substantially to the diameter of thepiston in order to prevent the piston from l Also, a piston rod isusually cooking in, the cylinder. employed to transmit the motion of thepiston to the adjacent cylinder, the rod having one end integral withthe piston and suitably attached to the adjacent cylinder.

The length of the rod and the piston land therefore determine to a greatextent the size to which the unit maybe manufactured.

Additionally, when conventional cylinder-piston units are employed toposition a member to selected locations which are closely spaced, forexample, twenty mils apart,

the tolerances involved in machining conventionalpiston cylinders becomequite close. As a result the cost of a conventional cylinderfpiston`unit increases when the 'f distance between positions decreases. v

Further, since themotion of one cylinder-piston unit is Atransmitted tothe adjacent unit through the piston rod, considerable care must bevexercised when the individual are arranged together to insure that theyact along va common axis. Otherwise the units tend to bind and'do notfunction properly.

It: hasbeen found in accordance w1th the present `invention that theabove-mentioned disadvantages may be overcome by providing acylinder-type adder wherein the Patented Aug-..91960,

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' A further object of thepresent invention i's to' provide a cylinderadder type mechanism for selectively position# ing a member to'any oneof'a plurality of closely spaced locations wherein the manufacturingtolerances vof the" mechanism are minimized. y ,n Q l A still furtherobject of the present .invention is 'to provide a cylinder adder typepositioning meclianisn'r'` wherein the individual yunits' arenotrequired'to act along "l a linear axis.

The foregoing and otherv objects',features and advan= tages of theinvention will ybe apparent-from vthe following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings.

In the drawings: f v

Fig, l is an enlarged view, partly in section, of a cylinder adder typepositioning mechanism lembodying the' present invention; i

Fig. 2 is an enlarged perspective view, partly in sectionf of one ofthecapsule units employed in the mechanism shown in Fig. il;

Fig. 3 is a view similar to Fig; 1 illustrating the position` ingmechanism in an actuated position; and 5 "y l Fig. 4 is a view similarto Fig. 1 illustrating a modi-v cation of the positioning mechanismshown in Fig.-l.

Referringto the drawings, and particularly'to Fig'. 1, the positioningmechanism comprises generally a plurality of movable capsule units 10,an output piston member 111 for transmitting the accumulated movement ofthe capsule units 10 to an output member indicated schematically as apointer `13, whichV is to be selectively positioned at"- any one of thepositions 14'indicated onthe scale 15.l

' The capsule 10 and the piston member 11 are mounted' provideanimprovedmechanism for positioning a member selectively to any one of a pluralityofl discrete positions. I lAnother object of the present invention is toprovide a compact cylinder adder type positioning mechanism.

for sliding movement in a suitablehousing 16. l

The capsule units 10 are similar so` only one is described in detail.With reference to Fig. 2, each capsule unit 10 comprises a cylindermember Z3, a hardenedprecision ball 24, and a cover 25 suitably securedto one end of the cylinder member 23. 'Ihe other end 26 is provided witha seat- 27 for receiving the precision ball 24, the curved line ofcontact 27L therebetween defining a iirst reference plane. The seat 21may be cir-v cular but `preferably has a conical or spherical shape asshown in the drawing. The distance D from the line of'contact Y27L ofthe Aball 24'and the conical seat 27 to the reference surface 28 ineffect determines the distance Xin Fig; 3 that the precision ball24fprotrudes lfrom the unit 10. As shown in Figs. l and 3 kthe cap` suleunits 10 are identical' except for'thedistance 'X. Y In this instancethe X distances form a mathematical progression of 1, 2, 4 and 5 whichallows the pointer 13 to be positioned at any one of the thirteenpositions* 0 through 12 of the scale 15.

In practice the distance X is controlled Aquite acA curately bycontrolling the distance D. Distance-DW is controlled' by iirstproviding the conical seat 27 and.-4 then machining the end 26 of thecylinder 23 until the distance X that the ball protrudes past themachined v reference surface 28 corresponds to the desired distance.

Since hardened precision steel balls may be obtained economically withtolerances of l 2 l06 and milling operations to tolerances of il' milare also quite economical to obtain, the fabrication of theY capsuleunitsV 10 are relatively inexpensive for discrete positioning de` viceswhere the motion transmitting ability of the smallest unit is in thevicinity of 2() mils.

Referring again to Fig. l, means are further provided for supplying uidpressure selectivelyv to each of the capsule units 10. This means, asshown, comprisesl a pump 31 having a pressure` supplyv conduit 32 andreturn conduit 33 which. are selectively connected to supply ports v34athrough 34d in the housing;16 through four separate three-way valves.35a through '35d vWhiclla are illustrated schematically in the drawing.If desired the valves 35 may be `actuated by means of solenoids (notshown) which are energized by a binary coded signal correspondingto, thedesired. positions 14 of4 pointers 13..

The positioning mechanism further includes means 37 for biasing the`capsule. units to a home position.. As shown in Fig. l this meanscomprises the piston mem.- ber 11 which `is disposed atthe output endVof the housing 16 and suppliedv with a constant uid. pressure. from asuitable valve 38 connected to the pressure supplyy conduit 32 of thepump 31. Other suitable biasing means knowny in thev art may be,employed if desired. Similarly, the positioning mechanism shown in Fig.1 may also be providedl with suitable. shockI absorbing meansV 39.Asshown this shock absorbingrmeans 39- comprises a capsule unit 40similar to the capsule units 10. Capsule unit 40 lis supplied withconstant pressure from pressure supply conduit 32- through Valve 41 andport 34e, this pressure being slightly greater than the biasing pressuresupplied to the piston member 11.

, Assuming that the capsule units are in the position shown in Fig. lwherein the valves 35 are positioned to connect each unit 10 to thereturn conduit 33 of the pump 31, that suitable pressures `are suppliedto the biasing means 37 and the shock absorbing means 39, andthat it isdesired to position'the pointer 13 to position 7 on scale 15, theoperation of the mechanism is as follows. Valves 34a, 34h, and 34e areactuatedv to the position shown in Fig. 3 which causes capsule units10a' through 10c to be supplied with pressure. The precision ball 24 ofcapsuleV 10a is moved to the conical seat Z7 and protrudes pastreference edge 28 the predetermined distance X corresponding to thedistance between scalepositions 14 on the scale 1.5. Similarly theprecision ball 24 of capsule 10b is moved to its conical seat 27 andprotrudes past its reference edge 28, a= distance corresponding to two.-full scale positions. Likewise the precision ball 24 of unit 10c extendspast its reference edge 28 a distance corresponding, to vfour scaledivisions. The total' displacement of the piston member 11 and thepointer 13 therefore corresponds to the sum of the individual dis--placements of the capsules.. It willthus be seen that any of the twelvepositions on the scaleY 15 may be obtained merely by actuating thevalves 35 inv various combinations.

Fig. 4 illustrates a modification of the positioning mech'- anism shownin Fig; l, and the same referencenumerals have been employedto designateidentical parts. In the embodiment shownA in Fig. 4 theVV piston member11 of Fig. l, which serves `the dual function of biasing the' capsuleunits 10` to a home position and of transmitting,

the accumulated motionof the individualv capsules 10- to the' pointer13, has been eliminated by reversing 'the posi*- tion of each of thecapsules 10 relative to their position in Fig. 1, and by modifying theend' capsule 10d. As shown inv Fig. 4 the end capsule 10d is providedwith av rod 4.4 which extends through. the housing 16 to theV pointer13. Capsule 10d therefore performsV the same function as the pistonmember 11: but allows the length ofthe mechanism to bev furtherlreduced. The operation of the mechanism shown in Fig; 4 is identical tothat shown in Fig. 1.

While the invention has been'. particularly shown and described withreference to preferred embodiments thereof,.it will be understood by;those skilled in the art that various'changes in formand details maybemade'therein without -departing from thel spiritV and` scope of. the'invention.

What is claimed' is:

l. A mechanism for selectively positioning an element to any one of'aplurality.l of discrete'positions'.comprising:

a plurality of capsule units', a.l housing mountingsaid units.inrseriallm'otion transmitting relationship, biasing means.

disposed in said'. housing` urging said` units to a; home positionwherein adjacent units are in contact, a ball disposed for rollingengagement in each capsule unit and arranged to protrude past an openend of said unit a predetermined distance to move succeeding -units acorresponding amount, pressure supply means connected to each unit,means for controlling said supply means to cause selective movement ofeach said ball to a protruded position, and means mounted Yfor movementwith the last capsule unit for transmitting the cumulative motion ofsaid units to said element.

2. A mechanism for selectively positioning an element to any one of aplurality of discrete positions comprising: a plurality of capsuleunits, a housing mounting said units in serial motion transmittingrelationship, biasing means disposed in said housing urging said unitsto a home position wherein adjacent units are in contact, a balldisposed for rolling engagement in each capsule unit and arrangedtoprotrude past an open end of said unit. a predetermined-distance tomove succeeding units. a` .corresponding amount in response to fluidpressure supplied to said capsule unit, pressure supply meansvconnectedto each unit, means. for controlling. said supply meansy tocause selective movement of each said ball to a protruded position, `andmeans mounted in motion trans.- mitting relationship between saidbiasing means and said element for transmitting the cumulative motion ofsaid units to said element.

3. The combination recited in claim 2 wherein said capsule units areidentical except for their length.

4. Thecombination recited in claim 2 further comprising means disposedin said housing for labsorbing im-' pact shocks between adjacent units.

5. A mechanism for selectively positioning anelement ing for urging saidunits to 1a home position` wherein.l

adjacent units are in cont-act and for maintaining said. units in motiontransmitting relationship relative to each other, means mounted formovement with the last capsule unit for transmitting the cumulativemotion of saidA units to said element, aball disposed in roll-ingengagement with the cylindrical bore of each capsuleunit `and arranged'to protrude past the open endofsaid unit to move the succeeding units apredetermined. distance corresponding to a predetermined multipleof lthespacing between adjacent said discrete positions in response to.E uidpressure supplied selectively to saidy capsule units, each unitincluding Ia pair of reference planes normal to the axis of said bore todetermine the movement Aimparted to succeeding units by aselected unit,l,a seatV presenting: a` circular line ofcontact disposedinone of saidreference planesv for receiving said ball when said` unit ispressurized, an accurate surface at the open end of. said unit definingthe other reference plane, andY meansV for supplying fluid pressure to.each of. said units-selec,- tivelywhereby said element is moved toY oneyof said ,discrete positions.

6:. A mechanism for-positioning an element vto any' oneof a plurality ofdiscrete positions comprising;` a plurality of capsule units, each ofsaidA units including, a capsule having a closed end andan open4 end, aicylindrical bore extending therebetween, a ball disposed in. saidY boreVin rolling engagement with the'. cylindrical surface of said bore,means for' supplying pressure to said bore tomove said ball to said openend, a; conical seat disposed at said open end coaxially with saidvboreYfor receiving-.said ball, the line of: contact therebetweeny defining;ar rst reference plane,y said seat having a diameter relative. to saidball to allow a portion of said ball to extend pastf saidrst referenceplane av predetermined amount; and @Il illrate' referencev surfacey on:the open end ofi said YJ,... i.

5 capsule disposed in a second reference plane normal to the axis ofsaid bore and spaced axially from said iirst reference plane a distancedetermined by the spacing of said `discrete positions, means mountingsaid capsule units in series along a path in cumulative motiontransmitting relationship with the accurate surface of one capsule unitadjacent the closed end of the succeeding unit, means biasing saidcapsule units to home position wherein said adjacent units are incontact, means for transmitting the movement of said capsules to saidelement, and means for selectively controlling the pressure supply meansof References Cited in the le of this patent UNITED STATES PATENTS1,561,341 Martin Nov. l0, 1925 2,197,867 Klement Apr. 23, 1940 2,699,757Tornkvist Jan. 18, 1955 2,714,906 1955 Peterson -v... Aug. 9,

